Great post from Pastor Zach Nielsen on Raising Kids in a Pornified Culture. His points:
1. Aim to give our kids a huge view of God who is gloriously delightful.
2. Teach them the gospel. Our kids are spring-loaded legalists.
3. Teach them that boundaries bring freedom and obedience is a blessing.
4. Talk to them sooner than later about sex and internet porn.
5. Begin to train your kids how to interact with the opposite sex.
6. Guard who your kids spend time with.
7. Guard the computer and turn off the television.
8. Seek to cultivate a relationship with your kids such that they feel they can be open with you about anything.
See his post for elaboration on each.